86 lines
3.6 KiB
Markdown
86 lines
3.6 KiB
Markdown
T0A – Power circuits and hazards: hazardous voltages, fuses and circuit breakers, grounding, electrical code compliance; Lightning protection; Battery safety
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- [[T0A01]] (B)
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Which of the following is a safety hazard of a 12-volt storage battery? #card
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- A. Touching both terminals with the hands can cause electrical shock
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- B. Shorting the terminals can cause burns, fire, or an explosion
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- C. RF emissions from a nearby transmitter can cause the electrolyte to emit poison gas
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- D. All these choices are correct
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- [[T0A02]] (D)
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What health hazard is presented by electrical current flowing through the body? #card
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- A. It may cause injury by heating tissue
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- B. It may disrupt the electrical functions of cells
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- C. It may cause involuntary muscle contractions
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- D. All these choices are correct
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- [[T0A03]] (B)
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In the United States, what circuit does black wire insulation indicate in a three-wire 120 V cable? #card
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- A. Neutral
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- B. Hot
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- C. Equipment ground
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- D. Black insulation is never used
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- [[T0A04]] (B)
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What is the purpose of a fuse in an electrical circuit? #card
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- A. To prevent power supply ripple from damaging a component
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- B. To remove power in case of overload
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- C. To limit current to prevent shocks
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- D. All these choices are correct
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- [[T0A05]] (C)
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Why should a 5-ampere fuse never be replaced with a 20-ampere fuse? #card
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- A. The larger fuse would be likely to blow because it is rated for higher current
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- B. The power supply ripple would greatly increase
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- C. Excessive current could cause a fire
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- D. All these choices are correct
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- [[T0A06]] (D)
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What is a good way to guard against electrical shock at your station? #card
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- A. Use three-wire cords and plugs for all AC powered equipment
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- B. Connect all AC powered station equipment to a common safety ground
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- C. Install mechanical interlocks in high-voltage circuits
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- D. All these choices are correct
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- [[T0A07]] (D)
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Where should a lightning arrester be installed in a coaxial feed line? #card
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- A. At the output connector of a transceiver
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- B. At the antenna feed point
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- C. At the ac power service panel
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- D. On a grounded panel near where feed lines enter the building
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- [[T0A08]] (A)
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Where should a fuse or circuit breaker be installed in a 120V AC power circuit? #card
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- A. In series with the hot conductor only
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- B. In series with the hot and neutral conductors
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- C. In parallel with the hot conductor only
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- D. In parallel with the hot and neutral conductors
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- [[T0A09]] (C)
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What should be done to all external ground rods or earth connections? #card
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- A. Waterproof them with silicone caulk or electrical tape
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- B. Keep them as far apart as possible
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- C. Bond them together with heavy wire or conductive strap
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- D. Tune them for resonance on the lowest frequency of operation
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- [[T0A10]] (A)
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What hazard is caused by charging or discharging a battery too quickly? #card
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- A. Overheating or out-gassing
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- B. Excess output ripple
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- C. Half-wave rectification
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- D. Inverse memory effect
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- [[T0A11]] (D)
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What hazard exists in a power supply immediately after turning it off? #card
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- A. Circulating currents in the dc filter
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- B. Leakage flux in the power transformer
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- C. Voltage transients from kickback diodes
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- D. Charge stored in filter capacitors
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- [[T0A12]] (B)
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Which of the following precautions should be taken when measuring high voltages with a voltmeter? #card
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- A. Ensure that the voltmeter has very low impedance
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- B. Ensure that the voltmeter and leads are rated for use at the voltages to be measured
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- C. Ensure that the circuit is grounded through the voltmeter
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- D. Ensure that the voltmeter is set to the correct frequency
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